Carbonaceous additive for molding sand



Patented July 7, 1953 CAR-BONACEOUS ADDITIVE SAND FOR Momma Edward H. King,'Cincinnati, and Joseph S. Schumacher, Mariemont, Ohio, assignors to The Hill I & Grilfith Company, Cincinnati, Ohio, a corporation of Ohio No'Drawing. Application June 1, 1951;

Serial N0. 229,546

I l. I

This invention relates to carbonaceous additives for foundary molding sands, and particularly, to a thermoplastic carbonaceous additive.

s Claims. (01. 22-188) Molding sands, in general, comprise various mix- Y 'tures of silica grains and clay particles to which may be added a wide variety of carbonaceous materials, such as seaco'al, gilsonite, high melting point coal tar pitch, asphalt, lignin, sawdust, wood flour, dextrine, farinaceous flour and gelatinized starch.

These carbonaceous additives, when utilized in varous combinations or proportions in a built or synthetic molding sand, impart molding and packing characteristics to the sand which are different from those which the sand would otherwise have, and also, determines to a substantial extent the physical and chemical, or thermal reaction of themold when the hot metal is poured into it. Although there are innumerable theories as to chemical and physical reactions of the various carbonaceous ingredients of molding sand when the metal is poured, the variety of the molding problems and the variety of the available carbonaceous additives has made it diflicult to formulate theories of any substantial scope as to proper blending practices. On this account, the selection of specific molding sand compositions for specific purposes has depended, for the most part, on empirical experiences and preferences which have developed in each particular foundry.

The present invention relates to an improvement in thermoplastic carbonaceous additives such asphalt and pitch which hereinafter will be termed bituminous plastic. Materials of this nature may be desirable in asynthetic mold sand either because of their adhesive characteristics which impart desirable molding characteristics to the sand prior to the pouring of the metal or because of chemical characteristics which impart desirable thermal properties to the mold when the metal is poured, or both. In any event,fo r,what ever reason the bituminous plastics are employed, one problem is. always present, namely, that of admixing the bituminous plastic with the molding sand.

Customarily, the bituminous plastic is ground up into pulverized condition and then physically mixed with the silica grains and clay, particles;

The ease with which this operation may. be per.- formed depends, of course, upon the discreteness of the grains or particlesofthe bituminous plastic. In order to avoid the":mai ntenance of the machinery for grinding thebituminous plastic in the foundry, where it would be used only occa-v sionally, it is desirable practice to grind the bituminous plastic at a point of manufacture then ship it in sacks or other containers to the foundry. I

where it may be stored and then used as needed.

This practice has the disadvantage that h s P1111 verized bituminous plastictends to set up in shipment or storage, particularly under pressure or if it gets warm, or both, that is, the grains or particles of bituminous plastic tend tostick together or congeal 'orcoalesce thereby making it dii'ficult to mix the supposedly pulverized plastic with thesand of the composition.

One of the objects of the present invention. is to provide a pulverized'bituminous plastic additive forgfoundry molding sand which retains its pulverulent condition both in shipment and in storage despite heat and pressure of the order to which it is apt to be exposed. Another object of the invention is to provide such carbonaceous additives which havegenerally desirable characteristics bothfrom thepoint'of view of forming the mold and of modifyingthethermal reaction of the mold when the metal is poured. In other words, it is the object of thisinvention to provide a pulverulent bituminous plastic for use in molding sand which has, atleast, all of the desirable properties which are characteristic of bituminous plastics, but which: retains its pulverulent form during shipment and'storage. Y

I have discovered that if furfural residue is blended with a pulverized bituminous plastic, the

tendency of the bituminous plastic to set up during shipment or storage is offset, and further, that both the molding and thermal characteristics of the sand-to which the mixture is added are also improved. 7

Furfural residue-is apartially carbonized cellulosic material'which is essentially acidic in its chemical reaction. Furfural residue is recovered from the manufacture of furfural and comprises approximately .equal'portions of soft carbon and cellulose;--A typical furfural'residue is that resulting from the manufacture of furfural according to the'process described in United States Patent N0.,'1,'735,084, issued November'12, 1929. Obviously, other cellulosic materials may be subjected-to conditions of temperature and acidity to provide'a mixture of soft carbon and cellulose :which is the equivalent of the furfural residue which is a by-product of the manufacture of furfural. Thus, the term furfural residue as used herein is intended to comprehend the members of a general class of partially carbonized.

having melting pointsoffrom 200 to 360 F., coal tar pitches having melting points of from 265 to 325? Fgboth melting points measured by the ball in ring method. Whenever desired, the bituminonsp'la'stics may be constituted by blending higher and .lower melting point bitumens to provide the desired characteristics.

In manufacturing the carbonaceous additive of this invention, the bituminous plastic and furfural residue are ground together in the desired. proportion to such fineness that 60'to'70 per fcent. of th ground materials pass a 50 mesh United States Standard screen sieve.

I have discovered that if as little as percent furfural residue is mixed with many bituminous c plastics to form an even homogeneous admixture,

then the materials may be shipped and stored in sacks or other containers without setting up or without the particles of bituminous plastic adhering one to another sufiiciently to interfere with" straight bituminous'plastics', but also have the added advantage of ready mixability, regardless of adverse conditions of shipment and storage. The above suggested proportion of bitumen to furfural residue is merely a general statement of the order of proper proportioning. The exact ratio which is suitable for any particular additive will depend upon' the-nature oi the ultimate molding operation and on the characteristics of the bituminous material selected. The point is tics and 'furfural residueypaclc better than a similar molding sand without the' 'furfural residue. Also, the acidity of the furfural residue beneficially controls the tendency of the clay particlesto swell in the presence of moisture. l When the hot metal is poured into a mold,

constituted by the sand grains, clay particles,

" bituminousiplastic and furfural residue, the

quick combustibility which is necessary to controlthefsa'ri'd expansion is provided by the furfural residuei- -Al's'o, when bituminous plastics are used without furfural residue there is a tendency for the inner surfaces of the mold to to use at least enough furfural residue to prevent the grains of bitumen from' amalgamating, but i not enough to impair the adhesiveness of the final product when used. While 10 per cent furfural residue content may be adequate for some bitumens, such as pitch, as much as'30 per cent furfural residue may be'necessary to properly protect some asphalts against amalgamation of particles. Likewise, the upper limit of amount of furfural residue which may be used depends on the nature of th bitumen and the nature of the molding operation. Thus, '70 per cent of the furfural residue is not absolutely the upper limit of the amount which may be used, provided the bituminous material is selected in relation to the molding operation so that f the admixture is suiiiciently adhesive in fact under the conditions under which it is actually used. w

As examples of mixtures which have proved satisfactory in commercial use, 60 parts'furfural residue by weight and 40 parts'of' petroleum byproduct asphalt of 250 F. melting pointiball in ring) are ground together to constitute a homogeneou admixture. Or 30 parts by weight furfural residue are similarly ground with 70 parts by weight high melting point coal tar pitch having a melting point of from 290 tov 310 F. (ball in ring).

These compositions have adVantages oVer straight bituminous plastics in many additional respects. In the first place, the presence of furfural residue tends to facilitate the intermixture of the asphalt and the sand grains, that .is, it tends to make them go together so that their masses interpenetrate more readily than if fur-v fural residue is not present. Additionally the be formed into cokelike masses by the hot metal. The furfural residue tends to prevent the formation of these cokelike niasses. The furfural residueitselr comprises fixed: carbons and carbons which are readily volatilized in desirable proper tionsl so that'its use inherently imparts balance to the characteristics of the molding sand;

It is also possible-to incorporate into a molding sandany otherudesired carbonaceous materials, in addition. to; the admixture of" bituminous plastic and. furfural residue. However, aspreparticular molding- "operation is .an empirical matter, in the sense .thatthere are, and can be, nostandards. In1all cases, the blend must be, and are, built .upqby choosing particular combination's 1 of silica =gr ains;- clay. particles, and carbonaceous additives. Thus, the, carbonaceous additive of this invention provides the, blender of: molding sands-with a unique bituminous plastic which is devoid of the Objectionablequalities of the previouslyavailable' bituminous plastics and-is .IJ'OSSBSSGd'i-Of positiveqand desirable characteristics of its ownn x Having described our invention, e; claim:

1. Aqcarbonaceous additive for molding sand, said additive. comprising to 30 percent pulverize'd bituminous plastic, by weight'and 10 to 70 per. cent pulverized iurfural residue said ,furfural residue being the solid residuary' product resultized furfural residuesaid furfural residue being 7 the solid residuaryproduct: resulting from the acid hydrolysis of pentosan' containing-material to form-furfural by weight mixed together to constitute a homogeneous body which does not cake in storage but has-adhesive properties when used 3. A carbonaceous additive for molding sand, said additive-comprising substantially 30 per-cent pulverized petroleum by-pro'duct asphalt. by weight and substantially. '70 per cent pulverized furfural residue said furfural' residue being the solid resid'uary product resulting from'the acid hydrolysis of pentosan containing. material to form furfural'by weight inixed't'ogether to constitute a homogeneous b'ody whichdoes not cake in storage but has-adhesive properties when used.

J EDWARD H; KING.

JO'SEPHS. SCHUMACHER.

Nolreference ;cited. 1 l 

1. A CARBONACEOUS ADDITIVE FOR MOLDING SAND, SAID ADDITIVE COMPRISING 90 TO 30 PER CENT PULVERIZED BITUMINOUS PLASTIC BY WEIGHT ND 10 TO 70 PER CENT PULVERIZED FURFURAL RESIDUE SAID FURFURAL RESIDUE BEING THE SOLID RESIDUARY PRODUCT RESULTING FROM THE ACID HYDROLYSIS OF PENTOSAN CONTAINING MATERIAL TO FORM FURFURAL BY WEIGHT MIXED TOGETHER TO CONSITUTE A HOMOGENEOUS BODY WHICH DOES NOT CAKE IN STORAGE BUT HAS ADHESIVE PROPERTIES WHEN USED. 